stmmac: add is_jumbo field to dma data

Optimize tx_clean by avoiding a des3 read in stmmac_clean_desc3().

In ring mode, TX, des3 seems only used when xmit a jumbo frame.
In case of normal descriptors, it may also be used for time
stamping.
Clean it in the above two case, without reading it.
Signed-off-by: Fabrice Gasnier <fabrice.gasnier@st.com>
Signed-off-by: Giuseppe Cavallaro <peppe.cavallaro@st.com>
Signed-off-by: Alexandre TORGUE <alexandre.torgue@st.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/stmicro/stmmac/chain_mode.c

@@ -152,7 +152,8 @@ static void stmmac_clean_desc3(void *priv_ptr, struct dma_desc *p)
 	struct stmmac_priv *priv = (struct stmmac_priv *)priv_ptr;
 	unsigned int entry = priv->dirty_tx;
 
-	if (priv->tx_skbuff_dma[entry].last_segment && !priv->extend_desc)
+	if (priv->tx_skbuff_dma[entry].last_segment && !priv->extend_desc &&
+	    priv->hwts_tx_en)
 		/* NOTE: Device will overwrite des3 with timestamp value if
 		 * 1588-2002 time stamping is enabled, hence reinitialize it
 		 * to keep explicit chaining in the descriptor.

drivers/net/ethernet/stmicro/stmmac/ring_mode.c

@@ -57,6 +57,7 @@ static int stmmac_jumbo_frm(void *p, struct sk_buff *skb, int csum)
 
 		priv->tx_skbuff_dma[entry].buf = desc->des2;
 		priv->tx_skbuff_dma[entry].len = bmax;
+		priv->tx_skbuff_dma[entry].is_jumbo = true;
 
 		desc->des3 = desc->des2 + BUF_SIZE_4KiB;
 		priv->hw->desc->prepare_tx_desc(desc, 1, bmax, csum,
@@ -76,6 +77,7 @@ static int stmmac_jumbo_frm(void *p, struct sk_buff *skb, int csum)
 			return -1;
 		priv->tx_skbuff_dma[entry].buf = desc->des2;
 		priv->tx_skbuff_dma[entry].len = len;
+		priv->tx_skbuff_dma[entry].is_jumbo = true;
 
 		desc->des3 = desc->des2 + BUF_SIZE_4KiB;
 		priv->hw->desc->prepare_tx_desc(desc, 0, len, csum,
@@ -89,6 +91,7 @@ static int stmmac_jumbo_frm(void *p, struct sk_buff *skb, int csum)
 			return -1;
 		priv->tx_skbuff_dma[entry].buf = desc->des2;
 		priv->tx_skbuff_dma[entry].len = nopaged_len;
+		priv->tx_skbuff_dma[entry].is_jumbo = true;
 		desc->des3 = desc->des2 + BUF_SIZE_4KiB;
 		priv->hw->desc->prepare_tx_desc(desc, 1, nopaged_len, csum,
 						STMMAC_RING_MODE);
@@ -126,7 +129,13 @@ static void stmmac_init_desc3(struct dma_desc *p)
 
 static void stmmac_clean_desc3(void *priv_ptr, struct dma_desc *p)
 {
-	if (unlikely(p->des3))
+	struct stmmac_priv *priv = (struct stmmac_priv *)priv_ptr;
+	unsigned int entry = priv->dirty_tx;
+
+	/* des3 is only used for jumbo frames tx or time stamping */
+	if (unlikely(priv->tx_skbuff_dma[entry].is_jumbo ||
+		     (priv->tx_skbuff_dma[entry].last_segment &&
+		      !priv->extend_desc && priv->hwts_tx_en)))
 		p->des3 = 0;
 }
 

drivers/net/ethernet/stmicro/stmmac/stmmac.h

@@ -47,6 +47,7 @@ struct stmmac_tx_info {
 	bool map_as_page;
 	unsigned len;
 	bool last_segment;
+	bool is_jumbo;
 };
 
 struct stmmac_priv {

drivers/net/ethernet/stmicro/stmmac/stmmac_main.c

@@ -1361,6 +1361,7 @@ static void stmmac_tx_clean(struct stmmac_priv *priv)
 		}
 		priv->hw->mode->clean_desc3(priv, p);
 		priv->tx_skbuff_dma[entry].last_segment = false;
+		priv->tx_skbuff_dma[entry].is_jumbo = false;
 
 		if (likely(skb != NULL)) {
 			pkts_compl++;